This invention involves an apparatus and process for applying a superconductive layer on an elongate substrate in a heating zone.
The effects of superconductivity have been known for a long time. The presence of a superconductor virtually negates the presence of resistance, below a certain critical temperature, thereby allowing direct current to flow unhindered by power losses. The critical temperature is 18.2 degrees Kelvin, for example, for the material Nb3Sn where helium is used as the cooling agent. When electric current passes through a superconductor, there is virtually no power loss. However, a significant problem is the creation and maintenance of the very low critical temperatures required by typical superconductors.
An alternative is the use of high temperature superconducting materials xe2x80x9cHTSLxe2x80x9d, which have a critical temperature of over 11 degrees Kelvin. These high temperature superconducting material xe2x80x9cHTSLxe2x80x9d materials can include such components as Yttruim, Barium, copper and oxygen. The high temperature superconducting material xe2x80x9cHTSLxe2x80x9d materials can be applied to a substrate, for example, by means of a pulsed laser beam, plasma evaporation, thermal evaporation or chemical treatment with heating of the substrate.
One procedure is described in DE 42 28 573 C1, where high temperature superconducting xe2x80x9cHTSLxe2x80x9d sections of good quality can be produced on a repetitive basis. The coating is intermittently struck with a pulsed laser beam. This results in a homogenous application of temperature for the substrate and the sections of the coating that have been struck by the intermittent laser pulse. A significant problem with this approach is that the current load-carrying capacity of the superconductive layer on the substrate is small and this process is only feasible due to the low separation rate with a low speed of application.
A number of attempts have been made to increase of the current load-carrying capacity of the produced high temperature superconducting xe2x80x9cHTSLxe2x80x9d section, such as that described in DE 197 27 343 A1, where a method of producing a high-temperature superconductive coating on an elongated substrate is disclosed. The method includes the steps of drawing the elongated substrate through a deposition chamber, heating the elongated substrate in a heating zone in the deposition chamber, coating the elongated substrate with high-temperature superconducting material in the heating zone to produce a superconductive elongated substrate, the superconductive coated elongated substrate having a first non-flat geometric form during the coating step, cooling down the substrate with the superconducting coating, and bending the superconductive coated elongated substrate into a second geometric form, which differs from the first geometric form, thereby producing a compressive strain in the superconductive coating and a capacity to carry higher current in the coating of the second geometric form than in the coating of the first geometric form, while retaining superconductivity.
With this procedure, the superconducting material is first applied to the substrate in one geometric form and then bent into a second geometric form after cooling. This will substantially increase the current load-carrying capacity of the high temperature superconducting material xe2x80x9cHTSLxe2x80x9d. However, this is a very slow procedure with a maximum coating rate of 10 millimetersxc3x97centimers2/second. When you increase the rate of applying the laser pulses, the performance parameters associated with the high temperature superconducting material xe2x80x9cHTSLxe2x80x9d will denigrate.
Another procedure is disclosed in EP 0 469 603 A2, where a first mirror deflects the laser beam in one direction and a second mirror deflects the laser beam in another direction perpendicular thereto to perform two dimensional scanning of the target. The two mirrors can be adjusted by electromagnetic drives in such a way that the laser beam can strike the entire target reducing the comsumption of superconductive material on the surface of the target. This procedure is very complex and the coordination of the two mirrors is fraught with trouble.
The present invention is directed to overcoming one or more of the problems set forth above.
In one aspect of this invention, a process for applying a superconductive layer on an elongate substrate is disclosed. The process includes moving the elongate substrate through a heating zone, applying a pulsed laser beam against a target, having a length, that is coated with superconductive material wherein particles of superconductive material are separated from the target and strike the elongate substrate with a plasma beam in the heating zone, and oscillating the pulsed laser beam across the target to provide a substantially uniform coating of superconductive material on the elongate substrate.
In another aspect of this invention, an apparatus for applying a superconductive layer on an elongate substrate is disclosed. The apparatus includes a deposition chamber having a heating zone through which an elongate substrate can be moved, a laser that can apply a pulsed laser beam, a target, having a length, that is coated with superconductive material, and an oscillating mechanism to move the pulsed laser beam across the target, wherein particles of superconductive material can be separated from the target and strike the elongate substrate with a plasma beam in the heating zone to provide a substantially uniform coating of superconductive material on the elongate substrate.
Still another aspect of this invention, the oscillating of the pulsed laser beam across the target includes directing the pulsed laser beam to a laser beam deflector that can reflect the pulsed laser beam across the length of the target.
Yet another aspect of this invention, further includes rotating the target at least one hundred and eighty degrees.
The above aspects are merely illustrative examples of an infinite number of aspects associated with this invention and should by no means be deemed limiting in any manner whatsoever.